exhaust

i am fairly new at cars i was wondering how hard it would be to put in new a header and a new cat back exhaust can someone tell me

There is no pat answer for this one. It depends on the car......how accessible is the exhaust manifold? Is there enough room around it for removal and header installation?
On older Hondas where the exhaust manifold faces the front of the car it's not too bad of a job. The newer ones, 2.4l for example, have the manifold towards the rear which makes it a bit tougher. I hope this helps.